JJB236

Correct tire pressure according to the manual is

front 34
back 42

Is this when the tires are cold or hot?

My 18 year old E-class Benz gas flap indicates the pressure at both cold and hot. Our cars are sports cars that need precision, and why is that manufacturers fail to indicate it?

jhbrennan

Check your owner's manual - I believe it says "Tire Pressures for Cold Tires" on page 5 or somewhere early in the manual.

ADias

Tire pressures are ALWAYS set cold.

34/42 seems high. Isn't it 33/39PSI w/ light load?

mdrums

2005-08 Carrera S COLD tire pressure is 33 front 39 rear. This is for 2 passengers and 1 suitcase. Cold tire pressure is based at 68 degree F. This is all in the owners manual.

Edgy01

Cars routinely cite a tatget pressure and it is ALWAYS cold. (Citing a pressure WARM or HOT is WAY too imprecise because pressure is a FUNCTION of temperature). Standard day temperature is always 68ºF or 20ºC. Standard lapse rate for altitude is 2ºC per thousand feet (per ICAO and FAA).

_Nathan

PV = nRT

ADias

As far as altitude... as one climbs up one needs to readjust pressure too, still maintaining internal tire pressure (cold) at 33/39.

brendo

nathan, i'm with you. pervert equals nert. of course, i'll just post something for edgy if i have a doubt. i'm a recovering engineer. doing that equation would constitute a relapse.

then again i can always ask mike to read the manual for me

Sadiq

My high school chemistry teacher cleaned it up for me and called it Pivnert... if only I had known back then...

ADias

Note that T is deg Kelvin - T=(278 + t) where t is in Centigrade.

Craig B

I seem to recall this is supposed to be the MINIMUM pressure - but there is no mention of what the maximum (or even preferred) pressure should be.

19_hole

"Note that T is deg Kelvin - T=(278 + t) where t is in Centigrade. "

I sorry to correct you but the proper conversion from Celcius to Kelvin is C+273.15=K

I also set the pressures for my '09 @ 37 Front, 44 Rear with the 19" wheel option.

BobbyB

Woo hoo, can we just fill out tires when cold? 68F or so, I promise

f4 plt

I just went out and double checked the placard in the door of my '09 C2S and it states cold tire pressure is 37 front and 44 rear. Just drove over 850 miles in one day in the car and watched the pressure with outside temps at or around 55-65 degrees the pressure increased by 2-3 lbs per corner. I have straight air in the tire although I want to change to nitregen (sp)

Carrera Mike

In your manual too, it say that if you're by yourself with no significant cargo, pressure is 33 Front, and 39 Rear.